英文:
Merge 2 csv files by common column
问题
我有2个CSV文件，分别是first.csv和second.csv。它们都有一个共享的列。
示例：
first：a b c d
second：x y a z
我必须创建一个第三个CSV文件，看起来像这样：
third：a b c d x y z
这些文件的条目数量不同，我只能合并具有相同列的行。
此外，这3个CSV文件的路径必须作为参数传递。
我尝试在Java中做这个，但Python也可以！
我真的不知道该怎么做:(
英文:
I have 2 csv files first.csv and second.csv. They both have a shared column.
Example:
first : a b c d
second: x y a z
I have to create a third csv file that looks like this:
third : a b c d x y z
The files do not have the same number of entries, I must only merge the lines that share the same column.
Also the paths of the 3 csv files must be sent as parameters.
I was trying to do this in Java but Python would also work!
I don't really know what I should do 
答案1
得分: 1
如果它们始终只有一个共享列，并且您想合并具有该列中相同值的记录（行），那么以下代码可能对您有所帮助：
```python
import pandas as pd
def merge_csv_files(first_file_path, second_file_path, output_file_path):
first_df = pd.read_csv(first_file_path)
second_df = pd.read_csv(second_file_path)
shared_column = set(first_df.columns) & set(second_df.columns)
# 寻找确切的一个共享列
if len(shared_column) != 1:
raise ValueError("CSV 文件没有恰好一个共享列。")
shared_column = shared_column.pop()
merged_df = pd.merge(first_df, second_df, on=shared_column, how='inner')
merged_df.to_csv(output_file_path, index=False)
first_file_path = 'first.csv'
second_file_path = 'second.csv'
output_file_path = 'third.csv'
merge_csv_files(first_file_path, second_file_path, output_file_path)
英文:
If they will always have exactly 1 shared column and you want to merge the records (lines) that have the same value in that column, then the following code might help you:
import pandas as pd
def merge_csv_files(first_file_path, second_file_path, output_file_path):
first_df = pd.read_csv(first_file_path)
second_df = pd.read_csv(second_file_path)
shared_column = set(first_df.columns) & set(second_df.columns)
# look for exactly 1 shared column
if len(shared_column) != 1:
raise ValueError("The CSV files do not have exactly one shared column.")
shared_column = shared_column.pop()
merged_df = pd.merge(first_df, second_df, on=shared_column, how='inner')
merged_df.to_csv(output_file_path, index=False)
first_file_path = 'first.csv'
second_file_path = 'second.csv'
output_file_path = 'third.csv'
merge_csv_files(first_file_path, second_file_path, output_file_path)
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